Sheet-metal oil-burning air heater



- 1619,56? March 1 1927. W. B. CROAN .I

`SHEET METAL OIL BURNING AIR HEATER Filed Jan.18. 192e s sheets-sheet 1 March 1 1927".`

w, B. cRoAN SHEET METAAL OIL.BURNING AIR HEATR s sheets-sheet 2 Filed Jari. 18, 192e lillllllllll Hlm March 1, 1927. 1,619,567

. w. B. CROAN SHEET METAL OIL BURNING AIR HEATER Filed Jan. 18. 1926 s sheets-sheet im 7 M Patented Mar. 1,-19127. i

UNITED STATES *1,619,561 PATENT OFFICE.

WALTER B. CROAN, OF CHICAGO, ILLINOIS, ASSIGNOB T0 DRYING SYSTEMS, INC., OF

CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SHEET-METAL 0ILBURNING AIR HEATER.

'Application led January 18, 1926. Serial No. 82,026.

The purpose which it is desired to accomplish by means of this invention is mainly to provide a successful and elicient air heating device using oil as a fuel while not requiring a combustion chamber of yrefractory material or other material which retains such a considerable amount of heat that its life is shortened and it is subject to disintegration, the combustion chamber of the 'present device being a tube of sheet metal around which air is caused to travel at the correct rate for insuring a safe temperature of the tube irrespective of the immense amount of heat which is transmitted thereby and radiated therefrom. Also by means of the present arrangement the tube is kept at the proper temperature to insure constant and eficient combustion without chilling the flame down to the point where carbon will be deposited. Another aim of the invention is to provide a combustion chamber permitting maximum radiation of heat from its exterior surface so that the heater maybe provided with the minimum of heating surface in proportion to the work performed. Other purposes of the Vinvention are to provide a maximum heating surface within the overall dimensions of the device without interfering with convenient assembly thereof while alsopermitting easy access to the lines for the burned gases.

These objects are successfully accomplished by a construction as shown in the drawings, wherein:

Figure 1 is a longitudinal sectional view in elevation of the 'oil burning air heater.

Fig. 2 ,is a plan view with the top cover sheet removed.

Fig. 3 is a front elevation.

Fig. 4 is a sectional view taken on the line 4 4 of Fig. 1.

The construction illustrated in the drawings, is practically wholly formed from sheet metal except Where angle irons are necessary for strength and that the casing is formed of blocks of magnesia surrounded by sheet metal for receiving a suitable finishing surface. The only sheet metal found which is `capable of withstanding the conditions of operation, of this `ap paratus is an alloy consisting of iron and chromium. One material suitable for the purpose, principally for the combustion tube is known asduralloy, the characteristics of which are very different from ordinary steel as it is only to a very slight degree susceptible to oxidation under normal conditionscooled from high temperature and is softened by sudden chilling. The sheet metal combustion tube is made the subject matter of a co-pending ap lication for patent, Serial No. 131,889, fileld August 27, 1926.

The combustion chamber 1 as shown in the drawings, consists of this material rolled into tubular form, with the meeting edges joined together either by butt-welding or bent over each other to form a seam. At the front end of the combustion chamber is a suitable casting 2 for closing the same ex-v cept for the inlet air passages and the Venturishaped atomizing chamber 3. This chamber is formed by a cylidrical extension 4 of the casting 2 and is lined with a refractory material 5. The fuel atomizing nozzle Gis supported on the front of the casting 2. The rear end of the combustion chamber is open to a hot gas passageway 7 communicating with a tier of horizontally' extending narrow flue-gas passageways 8. At their p then traveling in a reverse direction through the passageways 12 into a vertical air passageway 14 at the rear end of the structure. The air passageway 14 at its lower end communicates with a hot air chamber 15 sur-. rounding the combustion chamber 1. The heated air is finally conducted out of the apparatus through the conduit 16 at the bottom thereof.

The heat of the burning oil in the combustion chamber 1 is suicient to soon destroy the tube and other parts of the structure if it were not for the cooling action of the air traveling through the apparatus and around the combustion tube oppositely to the direction of How of the burned gases. It is therefore essential thatl when the oil burner is set into operation that the required ow of air be at once initiated and into contact with surfaces of continuously lessened temperature. Therefore, the'maximum amount of heat is extracted from the l combustionsgases since, although these gases combustion chambers lined with refractory material and of course lhaving a greatly lessened capacity for heat radiation possible with the sheet metal structure.

In the operation of the device, the air to f be heated 1s -irst set in motion or at least simultaneously with the ignition of the fuel, and of course during the normal operation of the oil burner, must at all times be pumped through the apparatus at the reuired rate to keep the sheet metal surfaces t ereof at a safe temperature. The air enters through the inlet 13 traveling along the set of passageways 11 and then the set 12, downwardly through the passageway 14 and into the llchamber 15 where it rises due to its temperature and flows around the combustion tube 1 and finally downward at the front end of the apparatus and out through the passageway 16, from which the heated air is conducted to the place of use thereof. The products of combustion leave the tube l at its rear end traveling in an opposite direction upwardly through the passage 7 and then' along the passageways 8 and 9 to the cooled gas outlet 10.

By the arrangement shown, the heated air is successively subjected to higher and higher temperatures while the, oppositely flowing combustion gases successively come may be considerably cooled when nearing the outlet, they-are then in contact with the surfaces subjected to the cooling action ofthe air when at its lowest temperature.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of this invention.

I claim:

1. An oil burning air heater comprising a sheet metal structure forming a combustion chamber anda plurality of narrow -flue gas passageways communicating with the combustion chamber andalternating with narrow passageways for air, means forming an air space surrounding the combustion chamber, and said air space being in communication with 'said air passageways.

2. An oil burning air heater comprising a sheet metal structure forming a combustion chamber land a plurality of narrow flue gas passageways communicating with the combustion chamber and alternating with narrow passageways for air, means forming an air space surrounding the combustion chamber, said air space being in communication with said air passageways, air intake means communicating with said narrow passageways for air and air outlet means communicating with the space surrounding the combustion chamber.

Signed at Chicago this 8th` day of January, 1926.

' WALTER B. cRoAN. 

